1. Field of the Invention
The present invention relates to a method and apparatus for transferring data in volatile and non-volatile redundant memory architectures, including random access and write cache architectures, and more particularly, to a method and apparatus for transferring data between a volatile memory and a non-volatile memory in a redundant storage environment.
2. Description of the Related Art
In a client/server environment, it is often required that write transactions cached by a server are kept in memory until transferred to stable storage. As this information may be critical such volatile memory modules usually require batteries or any other uninterruptible power supply for proper operation. In conventional systems, either the volatile memory module battery supplies power all the time, regardless of changes in system power, or the volatile memory module battery supplies power during an entire power failure time period.
Referring to FIG. 1, a conventional volatile memory module, including a central processing unit 1, a volatile memory 2, a non-volatile memory 3, or otherwise a main storage device 3, and an uninterruptible power supply 4 is illustrated. In the conventional module, the processing unit, the non-volatile memory and the main storage device are connected to each other. A battery or other uninterruptible power supply backs up the volatile memory. Because the battery backing up the volatile memory is not under any control, except possibly being controlled to supply power during an entire power failure time period, it remains on until the battery itself loses power or until power is restored.
Therefore, the volatile memory always remains powered up. However, the longer the battery is required to stay on before system power is restored, the more the life of the battery will be shortened. If the battery is required to maintain power for too long before system power is restored, the battery can lose power, thereby causing a loss of data stored in the volatile memory.
The concept used in the system described in FIG. 1 is used in the industry in a variety of implementations. In modem computing systems, as well as storage devices, the concept of redundancy has long been introduced. However, the concepts of reducing the hazards of data loss due to power supply failure have remained essentially the same. Systems currently available for handling power supply failures do not take advantage of the redundancy features of modem system to reduce the power requirements from the uninterruptible power supply.